This application relies for priority upon Korean Patent Application No. 2000-73012, filed on Dec. 4, 2000, the contents of which are herein incorporated by reference in their entirety.
1. Field of the Invention
The present invention relates to a semiconductor wafer processing system, and more particularly to a real time parameter monitoring apparatus for a high voltage chamber in the semiconductor wafer processing system.
2. Description of the Related Art
As the elements of a semiconductor device become smaller and more densely integrated, more precise wafer manufacturing techniques are required since the margin of error is greatly reduced, and even microscopic errors or defects can result in the production of inferior quality or poorly performing wafers.
In a conventional semiconductor wafer processing system, an ion implanter is widely used. Ion implanters use a high energy source to accelerate ionized dopant particles to a very high speed to thereby implant the accelerated dopant into a masked surface of a wafer. Ion implanters are widely used because they can correctly and easily control the quantity and distribution of impurities or dopants that are added. Examples of the ion implanters are disclosed in U.S. Pat. No. 5,834,786 by White et al., issued on November, 1998 and entitled xe2x80x9cHigh Current Ribbon Beam Ion Implanterxe2x80x9d; U.S. Pat. No. 5,883,393 by Tien et al., issued on November, 1999 and entitled xe2x80x9cSource Inner Shield For Eaton NV-10 High Current Implanterxe2x80x9d; and U.S. Pat. No. 6,084,240 by Lin et al., issued on January, 2000 and entitled xe2x80x9cIon Implanterxe2x80x9d.
FIG. 1 illustrates a general ion implanter 10. The ion implanter 10 comprises a high voltage chamber 11, a process chamber 16, and a load lock chamber 18. The high voltage chamber 11 includes a source chamber for producing ion beams, and a beam line chamber for controlling the strength of beams and accelerating them. The source chamber is insulated from the beam line chamber, and there is a large potential difference between the source chamber and the beam line chamber, on the order of about 40 kV. The beam line chamber is insulated from ground and has very high potential difference relative to ground, on the order of about 200 kV to ground.
In a semiconductor wafer process system using ion implantation techniques, the goal is to improve the efficiency and accuracy of the ion implantation, while maintaining the quality and uniformity of the ion implantation without increasing process costs.
To improve the efficiency and accuracy of the ion implantation, various INPUT parameters are measured, including wafer revolutions per minute (RPM), the voltage, the current, the pressure, and the temperature in the high voltage chamber, the amount of source gases, the mass of ion, the amount of ions, and the like. Preferably, these same parameters should be monitored in real time during the course of the ion implantation. This is because these parameters greatly affect the depth, accuracy and uniformity of the ion implantation process, which in turn greatly affects the characteristics of the semiconductor devices manufactured on the wafer.
However, in the past, the parameter values in the high voltage chamber could not be monitored in real time during the wafer manufacturing process. Instead, the parameter monitoring in the high voltage chamber was generally performed in the following manner. First the operation of the ion implanter was stopped. The high voltage chamber 11 was then opened to connect a plurality of measurement devices, such as the parameter measurement device 30 in FIG. 1, to parameter measurement sensors within the high voltage chamber 11. The parameter measurement device 30 was positioned at a safe distance from the high voltage chamber 11, and once the measurement devices were connected, the ion implanter was partially operated to measure the parameters through the parameter measurement device 30. Accordingly, an operator could ascertain certain values for the parameters in the high voltage chamber 11.
However, one significant drawback is that since the high voltage chamber 11 has a very high potential difference of 40 kV to 200 kV, an electrical arc could be generated, due to the potential difference between the high voltage chamber 11 and the parameter measurement device 30, when signals generated from the high voltage chamber are transmitted to the parameter measurement device 30. This electrical arc (as represented by the flash graphic in FIG. 1) sometimes severely damages the parameter measurement device 30.
Another drawback is that the ion implantation process must be stopped at regular intervals to take the measurements, which takes time and reduces throughput, which in turn increases per unit costs of production for the semiconductor devices.
In view of the foregoing, it is an object of the present invention to provide an improved parameter monitoring apparatus for a high voltage chamber in a semiconductor wafer processing system that can monitor parameters in the high voltage chamber in real time, thereby increasing the production rate of semiconductor wafers.
It is another object of the present invention to provide an improved parameter monitoring apparatus for a high voltage chamber in a semiconductor wafer processing system which can prevent parameter measurement devices from being damaged due to a potential difference between the high voltage chamber and the measurement devices during the parameter measurement.
To achieve these and other objects, the present invention provides a parameter monitoring apparatus for a high voltage chamber in a semiconductor wafer processing system, which includes an electrical-to-optical converter (xe2x80x9celectro-optical converterxe2x80x9d) for converting an electrical signal generated from the high voltage chamber into an optical signal. The apparatus also includes an optical-to-electrical converter (xe2x80x9copto-electrical converterxe2x80x9d) for converting the optical signal from the electro-optical converter into an electrical signal. The apparatus also includes at least one measuring device for measuring the electrical signal converted by means of the opto-electrical converter.
Preferably, the electro-optical converter includes an input circuit for receiving the signal generated from the high voltage chamber, an amplifying circuit for amplifying a current and a voltage of the signal from the input circuit, a modulation signal generating circuit for generating a modulation signal for modulating the amplified signal, a modulating circuit for modulating the amplified signal in response to the modulation signal, and an output circuit for converting the modulated signal into an optical signal and outputting the optical signal.
Preferably, the opto-electrical converter includes an input circuit for receiving the optical signal from the electro-optical converter and converting it into an electrical signal, a demodulating circuit for demodulating the signal from the input circuit to extract a wave form of an original signal therefrom, an offset adjusting circuit for adjusting an offset voltage of the demodulated signal, and an output circuit for outputting the demodulated signal having the adjusted offset voltage.